One type of internal combustion engines typically employ a number of cylinders which compress a fuel and air mixture such that upon firing of a spark plug associated with each cylinder, the compressed mixture ignites. The expanding combustion gases resulting therefrom move a piston within the cylinder. Upon reaching an end of its travel in one direction within the cylinder, the piston reverses direction to compress another volume of the fuel and air mixture. The resulting mechanical kinetic energy can be converted for use in a variety of applications, such as, propelling a vehicle or generating electricity, for example.
Another type of internal combustion engine, known as a compression ignition engine, uses a highly-compressed gas (e.g., air) to ignite a spray of fuel released into a cylinder during a compression stroke. In such an engine, the air is compressed to such a level as to achieve auto-ignition of the fuel upon contact between the air and fuel. The chemical properties of diesel fuel are particularly well suited to such auto-ignition.
The concept of auto-ignition is not limited to diesel engines, however, and has been employed in other types of internal combustion engines as well. For example, a self-igniting reciprocating internal combustion engine can be configured to compress fuel in a main combustion chamber via a reciprocating piston. In order to facilitate starting, each main combustion chamber is associated with a prechamber, particularly useful in starting cold temperature engines. Fuel is injected into not only the main combustion chamber, but also the combustion chamber of the prechamber, as well, such that upon compression by the piston, a fuel and air mixture is compressed in both chambers. A glow plug or other type of heater is disposed within the prechamber to elevate the temperature therein sufficiently to ignite the compressed mixture. The combustion gases resulting from the ignition in the prechamber are then communicated to the main combustion chamber.
Other types of internal combustion engines use natural gas as the fuel source and include at least one piston reciprocating within a respective cylinder. A spark plug is positioned within a cylinder head associated with each cylinder and is fired on a timing circuit such that upon the piston reaching the end of its compression stroke, the spark plug is fired to thereby ignite the compressed mixture.
In still further types of internal combustion engines, prechambers are employed in conjunction with natural gas engines. Given the extremely high temperatures required for auto-ignition with natural gas and air mixtures, glow plugs or other heat sources such as those employed in typical diesel engines, can be ineffective. Rather, a prechamber is associated with each cylinder of the natural gas engine and is provided with a spark plug to initiate combustion within the prechamber which can then be communicated to the main combustion chamber. Such a spark-ignited, natural gas engine prechamber is provided in, for example, the 3600 series natural gas engines commercially available from caterpillar Inc. of Peoria, Ill.
Spark-ignited engines typically have very high component temperatures. The temperature is a result of the gas flow and gas temperature characteristics. In particular, the surfaces defining the orifices of the nozzle of a member of a fuel combustion system, such as a prechamber, for example, can be subjected to very high temperatures. In the case of a prechamber assembly, the high temperatures can be caused by the velocity of the fuel/air mixture entering the nozzle through the orifices and the ignition flame front discharged from the nozzle out through the orifices. As a result, the high temperatures to which the orifices are subjected can cause degradation of the nozzle and impair the function of the nozzle over time.
U.S. Patent Application Publication No. 2013/0000598 is entitled, “Divided-Chamber Gas Engine,” and is directed to a gas engine that is configured to inject a combustion gas from an auxiliary combustion chamber through a plurality of nozzles, through which the auxiliary combustion chamber and a main combustion chamber are in communication with each other, so as to ignite a fuel in the main combustion chamber. An opening edge, at the auxiliary combustion chamber side, of each of the plurality of nozzles is formed to have a curved surface.
There is a continued need in the art to provide additional solutions to enhance the performance of a component of a fuel combustion system to improve its efficiency and useful life. For example, there is a continued need to protect the orifices of a nozzle of a prechamber assembly from the extreme temperature to which it can be subjected.
It will be appreciated that this background description has been created by the inventors to aid the reader, and is not to be taken as an indication that any of the indicated problems were themselves appreciated in the art. While the described principles can, in some respects and embodiments, alleviate the problems inherent in other systems, it will be appreciated that the scope of the protected innovation is defined by the attached claims, and not by the ability of any disclosed feature to solve any specific problem noted herein.